If the cost of the tablet was included in the price, then yes, you need to do something when the minimum term ends. It you only use it at home and have wifi and no need for mobile data, then you could cancel your contract. If you want some data when you're out, you might want to look at what other deals are available. If you have a mobile phone plan, you may be able to share data from it if you get the cheapest sim only deal, though that's generally poor value.
It does sound like you don't really need to keep paying and should cancel though, and just use wifi at home?
